SPATIAL AND TEMPORAL STABILITY OF CORN GRAIN YIELDS

y Year-to-year consistency of crop yields within a farm field is neede d to use grain yield monitor data for site-specific management decisio ns such as yield goals for fertilizer recommendations. A 5-yr study wa s conducted from 1991 to 1995 to determine whether patterns of corn (Z ea mays L,) grain yields are similar over a number of years and whethe r grain yields from one or more years can be used to predict grain yie lds for subsequent years, The experimental site was located at the Nor thern Cornbelt Sand plain Management Systems Evaluation Area near Prin ceton, MN. The research area was 4.4 acres with soils mapped as three variants of the Zimmerman fine sand (mixed, frigid, argic, Udipsamment ) and a Cantlin loamy fine sand (sandy, mired, frigid, typic, Udipsamm ent). Continuous corn was grown from 1990 through 1995 after alfalfa ( Medicago sativa L.) from 1981 through 1989, Cultural practices were ap plied uniformly to the 4.4 acre site each year, The 4.4 acres were div ided into 60 grid cells (50 ft. by 60 ft.) and grain yields, corrected to 15.5% moisture, were determined by hand harvesting an area (two ro ws 20 ft. long) within each of the 60 grid cells. Differences between highest and fewest continuous corn grain yields in the research area w ere 72 bu/acre in 1991, 44 bu/acre in 1992, 45 bu/acre in 1993, 51 bu/ acre in 1993, and 57 bu/acre in 1995. Grain yields were not spatially consistent from year to year. Areas with better grain yields were not consistent From year to year, and conversely, poor production areas we re not found in similar locations each year. Only 4 to 42% of the grai n yield variability for a given year is accounted for by a knowledge o f the grain yields from a previous year The lack of grain yield stabil ity as measured by ranked correlations on a sandy soil raises serious questions for the potential for use of this information, The data indi cate that the use of grain yield maps for fertilizer recommendations o n a site specific basis may not be possible or may require a much long er term database than the normally recommended 5 yr, unless there is a construct of inputs that explains the grain yield patterns each year.